1. Field of the Invention
The invention relates to a photothermal power generation device (TPV system) and method for generating power through thermophotovoltaic energy conversion for converting infrared rays (referred to as infrared radiation or heat rays as well) into electric power by means of a photoelectric conversion element (a photoelectric conversion cell).
2. Description of the Related Art
In a photothermal power generation device, an emitter is heated and emits infrared rays of a certain wavelength. The infrared rays impinge on a photoelectric conversion element and are converted into electric power. The photothermal power generation device has no movable portion and thus can realize a low level noise, low level oscillation system.
As an energy source in the forthcoming generation, photothermal power generation is advantageous in terms of cleanliness, silence, and the like. Combustion heat, solar heat, nuclear decay heat, or the like can be utilized to heat emitters. In general, however, combustion gas produced by burning a gaseous fuel such as butane is utilized to heat emitters.
In one known example, a photothermal power generation device is composed of an emitter made from a porous solid substance, emitter heating means designed to allow combustion gas to flow through the emitter, and a photoelectric conversion element for converting energy emitted from the emitter into electric energy.
In the above-described example, high-temperature combustion gas produced in a combustor (burner) flows through the emitter to heat it. However, combustion gas is dispersed unevenly when flowing through the emitter. This leads to uneven dispersion of rays of light emitted from the emitter. Such uneven dispersion is attributable to inadequate distribution of flame-rising portions in the combustor, incompatibility with the flow resistance in the emitter, changes in operational circumstances (the state of passage of combustion gas through the emitter changes depending on how a combustion chamber changes in response to a change in required power generation amount), and the like.
In the case where light is emitted from the emitter unevenly, the amount of incident energy differs among a plurality of photoelectric conversion cells for receiving light. For this reason, the power generation amount differs among these photoelectric conversion cells. As a result, the current value also differs among them, just as the power generation amount differs among them. Further, since the photoelectric conversion cells are generally connected in series, the total power generation amount is determined by a formula “the sum of voltages generated by the cells”×“the current flowing through the cell with the minimum power generation amount”. Thus, the current flowing through the cell with the minimum power generation amount has a low intensity if the degree of dispersion is sizable. As a result, a drop in power conversion efficiency occurs and causes a problem.